I didn't even get 40mpg in my Titanium, I surely don't expect to see it with the ST. Down a long, steep hill with a tailwind, maybe.

I can do that pretty routinely in my Ti at 65 MPH burning premium gas if I'm not going into a serious headwind. I've seen higher highway averages with winds at my back. It's amazing how quickly that average drops in stop and go traffic though. It will be interesting how (if?) Shelby does that 40 MPG in an ST for sure though.